1. Field of the Invention
This invention relates to a surface gap type igniter plug for use in various types of internal combusion engines, gas burner and the like, and particularly concerns to connecting structure between connector and metallic shell.
2. Description of the Prior Art
This kind of igniter plug has been introduced as of a low voltage surface gap type shown in FIG. 3 at (B) by way of illustration.
The igniter plug (B) has a plug body 100, a metallic barrel 200, a connector 300 and a sleeve terminal 330. The plug body 100 has a cylindrical metallic shell 110 into which an annular semi-conductor tip 120 and a tubular insulator 130 are serially located.
Into serial bores of the tip 120 and the insulator 130, is a center electrode 140 placed which consists of an insert axis 141 and a discharge tip 146 each serially connected by means of welding. A rear end of the insert axis 141 is redundantly projected from that of the insulator 130, and enclosed by an insulator tube 142. A sealant glass 150 is provided with a space between the center electrode 140 and the insulator 130 at the position in which the tip 146 and the insert axis 141 are welded. The metallic barrel 200 is securely connected to a rear end of the metallic shell 110 of welding as designated by numeral 160. The connector 300 has an insulator sleeve 310 interfit into an innerside of a metallic sleeve 320, the front end of which is brazed to a rear end of the metallic sleeve 320 of the metallic barrel 200 as seen at numeral 250. The insulator sleeve 310 has a diameter-reduced portion at its front end which extends into the rear end of the metallic barrel 200, and encloses the insulator tube 142. The sleeve terminal 330 is interfit between a rear portion of the insulator sleeve 310 and that of the insert axis 141, both the rear ends being arranged in flush with each other, and secured by means of brazing as seen at numeral 350.
The igniter plug (B) has been assembled in the following procedures.
(1) The plug body 100 is welded or brazed at 160 to the metallic barrel 200 after completed the plug body 100.
(2) The insulator sleeve 310 is inserted into the metallic sleeve 320, and brazed to the metallic barrel 200 as indicated by 250.
(3) The sleeve terminal 330 is brazed at 350 to the insert axis 141 while heat remained by the braze operation 250 is kept.
The above igniter, however, has disadvantages as follows:
Firstly, preceding procedures are rendered ineffective, once defects occur at the post procedure (3), thus leading to an increased cost.
Secondly, the procedure at (3) is done at a reduced space in the metallic sleeve 320, thus requiring well-trained and skilled technique.
Therefore, it is object of this invention to provide a surface gap type igniter plug which can be easily assembled with least defect, and making it possible to easily weld a sleeve terminal to a center electrode, at the same time, securing positive contact between the terminal and the electrode without introducing an insufficient contact therebetween.
Accordingly there is provided a surface gap type igniter plug comprising; a cylindrical metallic shell; a tubular insulator inserted into said metallic shell with a rear end projected from that of the insulator; a center electrode disposed to position at an innerside of the insulator, the electrode making its rear end projected from the rear end of the insulator; a sleeve terminal located between an outerside of the electrode and an innerside of the insulator, the terminal being secured at a rear end to the center electrode by means of welding; a connector having an insulator sleeve interfit into an innerside of a metallic sleeve, the insulator sleeve being terminated short of a front end of the metallic sleeve; and the connector being securely capped to the metallic shell at a time of assemblage with the rear end of the tubular insulator interfit into an innerside of the insulator sleeve, and with the metallic shell interfit into an innerside of the metallic sleeve.